Molecular oxygen is an essential nutrient for nonfacultative aerobic organisms, including humans. Oxygen is used in many important ways, namely, as the terminal electronic acceptor in oxidative phosphorylation, in many dioxygenase reactions, including the synthesis of prostaglandins and of vitamin A from carotenoids, in a host of hydroxylase reactions, including the formation and modification of steroid hormones, and in both the activation and the inactivation of xenobiotics, including carcinogens. The extensive P-450 system uses molecular oxygen in a host of important cellular reactions. In a similar vein, nature employs free radicals in a large variety of enzymic reactions.
Excessive concentrations of various forms of oxygen and of free radicals can have serious adverse effects on living systems, including the peroxidation of membrane lipids, the hydroxylation of nucleic acid bases, and the oxidation of sulfhydryl groups and of other sensitive moieties in proteins. If uncontrolled, mutations and cellular death result.
Biological antioxidants include well-defined enzymes, such as superoxide dismutase, catalase, selenium glutathione peroxidase, and phospholipid hydroperoxide glutathione peroxidase. Nonenzymatic biological antioxidants include tocopherols and tocotrienols, carotenoids, quinones, bilirubin, ascorbic acid, uric acid, and metal-binding proteins. Various antioxidants, being both lipid and water soluble, are found in all parts of cells and tissues, although each specific antioxidant often shows a characteristic distribution pattern. The so-called ovothiols, which are mercaptohistidine derivatives, also decompose peroxides nonenzymatically.
Free radicals, particularly free radicals derived from molecular oxygen, are believed to play a fundamental role in a wide variety of biological phenomena. In fact, it has been suggested that much of what is considered critical illness may involve oxygen radical (xe2x80x9coxyradicalxe2x80x9d) pathophysiology (Zimmermen J J (1991) Chest 100: 189S). Oxyradical injury has been implicated in the pathogenesis of pulmonary oxygen toxicity, adult respiratory distress syndrome (ARDS), bronchopulmonary dysplasia, sepsis syndrome, and a variety of ischemia-reperfusion syndromes, including myocardial infarction, stroke, cardiopulmonary bypass, organ transplantation, necrotizing enterocolitis, acute renal tubular necrosis, and other disease. Oxyradicals can react with proteins, nucleic acids, lipids, and other biological macromolecules producing damage to cells and tissues, particularly in the critically ill patient.
Free radicals are atoms, ions, or molecules that contain an unpaired electron (Pryor W A (1976) Free Radicals in Biol. 1: 1). Free radicals are usually unstable and exhibit short half-lives. Elemental oxygen is highly electronegative and readily accepts single electron transfers from cytochromes and other reduced cellular components; a portion of the O2 consumed by cells engaged in aerobic respiration is univalently reduced to superoxide radical (xe2x80xa2O2xe2x88x92) (Cadenas E (1989) Ann. Rev. Biochem. 58: 79). Sequential univalent reduction of xe2x80xa2O2xe2x88x92 produces hydrogen peroxide (H2O2), hydroxyl radical (xe2x80xa2OH), and water.
Free radicals can originate from many sources, including aerobic respiration, cytochrome P-450-catalysed monooxygenation reactions of drugs and xenobiotics (e.g., trichloromethyl radicals, CCl3., formed from oxidation of carbon tetrachloride), and ionizing radiation. For example, when tissues are exposed to gamma radiation, most of the energy deposited in the cells is absorbed by water and results in scission of the oxygen-hydrogen covalent bonds in water, leaving a single electron on hydrogen and one on oxygen creating two radicals H. and xe2x80xa2OH. The hydroxyl radical, xe2x80xa2OH, is the most reactive known in chemistry. It reacts with biomolecules and sets off chain reactions and can interact with the purine or pyrimidine bases of nucleic acids. Indeed, radiation-induced carcinogenesis may be initiated by free radical damage (Breimer L H (1988) Brit. J. Cancer 57: 6). Also for example, the xe2x80x9coxidative burstxe2x80x9d of activated neutrophils produces abundant superoxide radical, which is believed to be an essential factor in producing the cytotoxic effect of activated neutrophils. Reperfusion of ischemic tissues also produces large concentrations of oxyradicals, typically superoxide (Gutteridge J M C and Halliwell B (1990) Arch. Biochem. Biophys. 283: 223). Moreover, superoxide may be produced physiologically by endothelial cells for reaction with nitric oxide, a physiological regulator, forming peroxynitrite, ONOOxe2x88x92 which may decay and give rise to hydroxyl radical, xe2x80xa2OH (Marletta M A (1989) Trends Biochem. Sci. 14: 488; Moncada et al. (1989) Biochem. Pharmacol. 38: 1709; Saran et al. (1990) Free Rad. Res. Commun. 10: 221; Beckman et al. (1990) Proc. Natl. Acad. Sci. (U.S.A.) 87: 1620). Additional sources of oxyradicals are xe2x80x9cleakagexe2x80x9d of electrons from disrupted mitochondrial or endoplasmic reticular electron transport chains, prostaglandin synthesis, oxidation of catecholamines, and platelet activation.
Oxygen, though essential for aerobic metabolism, can be converted to poisonous metabolites, such as the superoxide anion and hydrogen peroxide, collectively known as reactive oxygen species (ROS). Increased ROS formation under pathological conditions is believed to cause cellular damage through the action of these highly reactive molecules on proteins, lipids, and DNA. During inflammation, ROS are generated by activated phagocytic leukocytes; for example, during the neutrophil xe2x80x9crespiratory burstxe2x80x9d, superoxide anion is generated by the membrane-bound NADPH oxidase. ROS are also believed to accumulate when tissues are subjected to ischemia followed by reperfusion.
Many free radical reactions are highly damaging to cellular components; they crosslink proteins, mutagenize DNA, and peroxidize lipids. Once formed, free radicals can interact to produce other free radicals and non-radical oxidants such as singlet oxygen (1O2) and peroxides. Degradation of some of the products of free radical reactions can also generate potentially damaging chemical species. For example, malondialdehyde is a reaction product of peroxidized lipids that reacts with virtually any amine-containing molecule. Oxygen free radicals also cause oxidative modification of proteins (Stadtman E R (1992) Science 257: 1220).
xe2x80xa2O2 can also react, at a diffusion-limited rate, with NO; yielding peroxynitrite (Huie et al. (1993) Free Rad. Res. Commun. 18: 195).
It is also known that superoxide is involved in the breakdown of endothelium-derived vascular relaxing factor (EDRF), which has been identified as nitric oxide (NO), and that EDRF is protected from breakdown by superoxide dismutase. This suggests a central role for activated oxygen species derived from superoxide in the pathogenesis of vasospasm, thrombosis and atherosclerosis. See, for example Gryglewski R J et al., xe2x80x9cSuperoxide Anion is Involved in the Breakdown of Endothelium-derived Vascular Relaxing Factorxe2x80x9d, (1986) Nature 320: 454-456 and Palmer R M J et al., xe2x80x9cNitric Oxide Release Accounts for the Biological Activity of Endothelium Derived Relaxing Factorxe2x80x9d, (1987) Nature 327: 523-526.
Aerobic cells generally contain a number of defenses against the deleterious effects of oxyradicals and their reaction products. Superoxide dismutases (SODs) catalyse the reaction:
2xe2x80xa2O2xe2x88x92+2H+xe2x86x92O2+H2O2
which removes superoxide and forms hydrogen peroxide. H2O2 is not a radical, but it is toxic to cells; it is removed by the enzymatic activities of catalase and glutathione peroxidase (GSH-Px). Catalase catalyses the reaction:
xe2x80x832H2O2xe2x86x922H2O+O2
and removes hydrogen peroxide and forms water and oxygen. GSH-Px removes hydrogen peroxide by using it to oxidise reduced glutathione (GSH) into oxidised glutathione (GSSG) according to the following reaction:
2GSH+H2O2xe2x86x92GSSG+2H2O
Other enzymes, such as phospholipid hydroperoxide glutathione peroxidase (PLOOH-GSH-Px), convert reactive phopholipid hydroperoxides, free fatty acid hydroperoxides, and cholesterol hydroperoxides to corresponding harmless fatty acid alcohols. Glutathione S-transferases also participate in detoxifying organic peroxides. In the absence of these enzymes and in presence of transition metals, such as iron or copper, superoxide and hydrogen peroxide can participate in the following reactions which generate the extremely reactive hydroxyl radical xe2x80xa2OHxe2x88x92:
xe2x80xa2O2xe2x88x92+Fe3+xe2x86x92O2+Fe2+
H2O2+Fe2+xe2x86x92xe2x80xa2OH+OHxe2x88x92+Fe3+
In addition to enzymatic detoxification of free radicals and oxidant species, a variety of low molecular weight antioxidants such as glutathione, ascorbate, tocopherol, ubiquinone, bilirubin, and uric acid serve as naturally-occurring physiological antioxidants (Krinsky N I (1992) Proc. Soc. Exp. Biol. Med. 200: 248-54). Carotenoids are another class of small molecule antioxidants and have been implicated as protective agents against oxidative stress and chronic diseases. Canfield et al. (1992) Proc. Soc. Exp. Biol. Med. 200: 260 summarize reported relationships between carotenoids and various chronic diseases, including coronary heart disease, cataract, and cancer. Carotenoids dramatically reduce the incidence of certain premalignant conditions, such as leukoplakia, in some patients.
In an effort to prevent the damaging effects of oxyradical formation during reoxygenation of ischemic tissues, a variety of antioxidants have been used. One strategy for preventing oxyradical-induced damage is to inhibit the formation of oxyradicals such as superoxide. Iron ion chelators, such as desferrioxamine (also called deferoxamine or Desferal) and others, inhibit iron ion-dependent xe2x80xa2OH generation and thus act as inhibitors of free radical formation (Gutteridge et al. (1979) Biochem. J. 184: 469; Halliwell B (1989) Free Radical Biol. Med. 7: 645; Van der Kraaij et al (1989) Circulation 80: 158). Amino-steroid-based antioxidants such as the 21-aminosteroids terms xe2x80x9clazaroidsxe2x80x9d (e.g, U74006F) have also been proposed as inhibitors of oxyradical formation. Desferrioxamine, allopurinol, and other pyrazolopyrimidines such as oxypurinol, have also been tested for preventing oxyradical formation in a myocardial stunning model system (Bolli et al. (1989) Circ. Res. 65: 607) and following hemorrhagic and endotoxic shock (DeGarvilla et al. (1992) Drug Devel. Res. 25: 139). However, each of these compounds has notable drawbacks for therapeutic usage. For example, deferoxamine is not an ideal iron chelator and its cellular penetration is quite limited.
Another strategy for preventing oxyradical-induced damage is to catalytically remove oxyradicals such as superoxide once they have been formed. Superoxide dismutase and catalase have been extensively explored, with some success, as protective agents when added to reperfusates in many types of experiments or when added pre-ischemia (reviewed in Gutteridge J M C and Halliwell B (1990) op.cit.). The availability of recombinant superoxide dismutase has allowed more extensive evaluation of the effect of administering SOD in the treatment or prevention of various medical conditions including reperfusion injury of the brain and spinal cord (Uyama et al. (1990) Free Radic. Biol. Med. 8: 265; Lim et al. (1986) Ann. Thorac. Surg. 42: 282), endotoxemia (Schneider et al. (1990) Circ. Shock 30: 97; Schneider et al. (1989) Prog. Clin. Biol. Res. 308: 913, and myocardial infarction (Patel et al. (1990) Am. J Physiol. 258: H369; Mehtaetal. (1989) Am. J. Physiol. 257: H1240; Nejimaetal. (1989) Circulation 79: 143; Fincke et al. (1988) Arzneimittelforschung 38: 138; Ambrosio et al. (1987) Circulation 75: 282), and for osteoarthritis and intestinal ischemia (Vohra et al. (1989) J. Pediatr. Surg. 24: 893; Flohe L. (1988) Mol. Cell. Biochem. 84. 123). Superoxide dismutase also has been reported to have positive effects in treating systemic lupus erythematosus, Crohn""s disease, gastric ulcers, oxygen toxicity, burned patients, renal failure attendant to transplantation, and herpes simplex infection.
An alternative strategy for preventing oxyradical-induced damage is to scavenge oxyradicals such as superoxide once these have been formed, typically by employing small molecule scavengers which act stoichiometrically rather than catalytically. Congeners of glutathione have been used in various animal models to attenuate oxyradical injury. For example, N-2-mercaptopropionylglycine has been found to confer protective effects in a canine model of myocardial ischemia and reperfusion (Mitsos et al. (1986) Circulation 73: 1077) and N-acetylcysteine (xe2x80x9cMucomystxe2x80x9d) has been used to treat endotoxin toxicity in sheep (Bernard et al. (1984) J. Clin. Invest. 73: 1772). Dimethyl thiourea (DMTU) and butyl-xcex1-phenylnitrone (BPN) are believed to scavenge the hydroxyl radical, xe2x80xa2OH, and have been shown to reduce ischemia-reperfusion injury in rat myocardium and in rabbits (Vander Heide et al. (1987) J. Appl. Physiol. 63: 2426). Mannitol has also been used as a free radical scavenger to reduce organ injury during reoxygenation (Fox R B (1984) J. Clin. Invest. 74: 1456; Ouriel et al. (1985) Circulation 72: 254).
Thus, application of inhibitors of oxyradical formation and/or enzymes that remove superoxide and hydrogen peroxide and/or small molecule oxyradical scavengers have all shown promise for preventing re-oxygenation damage present in a variety of ischemic pathological states and for treating or preventing various disease states associated with free radicals. However, each of these categories contains several drawbacks. For example, inhibitors of oxyradical formation typically chelate transition metals which are used in essential enzymatic processes in normal physiology and respiration; moreover, even at very high doses, these inhibitors do not completely prevent oxyradical formation. Superoxide dismutases and catalase are large polypeptides which are expensive to manufacture, do not penetrate cells or the blood-brain barrier, and generally require parenteral routes of administration. Free radical scavengers act stoichiometrically and are thus easily depleted and must be administered in high dosages to be effective.
The complex formed between the chelator desferrioxamine and manganese has SOD activity and has shown some activity in biological models but the instability of the metal ligand complex apparently precludes its pharmaceutical use. Porphyrin-manganese complexes have been shown to protect bacteria from paraquat toxicity and to promote the aerobic survival of SOD-deficient E. coli mutants. A class of manganese macrocyclic ligand complexes with SOD activity has also been described with one prototype reportedly showing protection in a model for myocardial ischemia-reperfusion injury (Black et al. (1 994) J. Pharmacol. Exp. Ther. 270: 1208).
WO94/13300 (and U.S. Pat. No. 5,403,834 and the related applications U.S. Ser. No. 08/380,731 and U.S. Ser. No. 08/479,697), U.S. Pat. No. 5,696,109, WO96/40148 and WO96/40149 each disclose salen-transition metal complexes, including salen-manganese complexes, such as salen-Mn (III) complexes of general formula 
wherein R1 to R4, Y1 to Y6, X1 to X4, A and n are as separately defined in each of the specifications referred to above, as having antioxidant and/or free radical scavenging properties; the compounds are indicated to have superoxide dismutase activity and/or catalase activity.
WO95/10185 and WO96/09053 disclose manganese porphyrin derivatives of general formula 
wherein R is as defined therein, as mimetics of superoxide dismutase.
WO96/39396 discloses manganese or iron complexes of nitrogen-containing fifteen-membered macrocyclic ligands of general formula 
wherein R1 to R9, R1xe2x80x2 to R9xe2x80x2, X, Y and M are as defined therein, as superoxide dismutase mimics.
It is therefore an object of the present invention to provide further compounds, in particular manganese complexes, which are SOD, CAT or POD mimetics and which are therefore of utility as prophylactic and therapeutic agents.
The present invention relates to compounds which are effective as superoxide dismutase (SOD), and/or catalase (CAT), and/or peroxidase (POD) mimetics and which, accordingly, have antioxidant and/or free radical scavenging properties and function as in vivo antioxidants. In particular the present invention relates to manganese complexes of bipyridine derivatives, pharmaceutical formulations containing them, processes for their preparation and intermediates in such processes, and the use of such compounds in prophylaxis and therapy.
The manganese bipyridine complexes can be represented by structural formula (I): 
In structural formula (I), X represents any suitable counter-anion; R1 and R2, independently, represent hydrogen, C1-6 alkoxy or nitro; R3, R4, R5 and R6 each, independently, represents hydrogen, hydroxy, halo, C1-6 alkyl, C2-6 alkenyl or C1-6 alkoxy; and R7, R8, R9 and R10 each, independently, represents hydrogen, hydroxy, halo, C1-6 alkyl, C2-6 alkenyl or C1-6 alkoxy. Solvates of the compounds of formula (I) are also included within the scope of the present invention.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.
Certain compounds of formula (I) can exist in stereoisomeric forms (e.g. they can contain one or more asymmetric carbon atoms or can exhibit cis-trans isomerism). The individual stereoisomers (enantiomers and diastereoisomers) and mixtures of these are included within the scope of the present invention. Likewise, it is understood that certain compounds of formula (I) can exist in tautomeric forms and these are also included within the scope of the present invention.
Suitable values for the various groups listed above within the definitions for R1 to R10 are as follows:
Halo is, for example, fluoro, chloro, bromo or iodo; preferably it is fluoro, chloro or bromo, more preferably fluoro;
C1-6 alkyl is, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, n-hexyl, isohexyl and sec-hexyl; preferably it is methyl, ethyl, isopropyl, tert-butyl and n-hexyl, more preferably methyl;
C2-6 alkenyl is, for example, ethenyl, propenyl, allyl, but-1-enyl, but-2-enyl, 2-methyl-prop-1-enyl; preferably it is ethenyl or allyl, more preferably allyl;
C1-6 alkoxy is, for example, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, sec-pentoxy, n-hexyloxy, iso-hexyloxy and sec-hexyloxy; preferably it is methoxy or ethoxy, more preferably methoxy.
The counter anion X can represent any suitable anion with which the complex of formula (I) can be formed. Suitable examples include halide, formate, acetate, propionate, butyrate, valerate, methoxide, ethoxide, PF6 or triflate. X is typically chloride, bromide, fluoride, methoxide or acetate. Preferably X represents acetate or chloride.
Mn is in the 3+ oxidation state in the compound of formula (I); also encompassed by the present invention are the compounds of formula (Ia) 
wherein R1 to R10 are as defined above, in which Mn is in the 2+ oxidation state.
Thus the phenyl ring carrying the groups R3 to R6 may be unsubstituted (where each of R3 to R6 represents hydrogen) or may be mono-, di-, tri- or tetra-substituted at any of the available positions of the ring with the other groups defined above for R3 to R6; where the phenyl ring is di-, tri- or tetra-substituted each of the substituents may be the same or may be different. Similar considerations apply in respect of the phenyl ring carrying the groups R7 to R10.
In an embodiment R1 and R2 independently represent hydrogen, methoxy or ethoxy; preferably R1 and R2 represent hydrogen.
In another embodiment R1 and R2 are identical.
In an embodiment at least one of R3, R4, R5 and R6 represents hydrogen.
In a further embodiment at least one of R7, R8, R9 and R10 represents hydrogen.
In a preferred embodiment at least one of R3, R4, R5 and R6 represents hydrogen and at least one of R7, R8, R9 and R10 represents hydrogen.
In a more preferred embodiment each of the phenyl rings are independently either unsubstituted or are mono- or di-substituted.
In an embodiment the phenyl ring carrying the groups R3 to R6 is substituted identically to the phenyl ring carrying the groups R7 to R10; identically in this context applies not only to the nature of the substituents but also to their positions.
In another embodiment the phenyl ring carrying the groups R3 to R6 is substituted non-identically to the phenyl ring carrying the groups R7 to R10; non-identically in this context has the opposite meaning to identically as defined above.
In another embodiment each of R3 to R6 represents hydrogen, hydroxy, fluoro, methyl, ethyl, isopropyl, tert-butyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In a preferred embodiment R3 represents hydrogen or methoxy, more preferably hydrogen.
In a preferred embodiment R4 represents hydrogen, fluoro, methyl, ethyl, isopropyl, tert-butyl, propenyl (especially allyl) or methoxy.
In a preferred embodiment R5 represents hydrogen, methyl or ethyl, more preferably hydrogen or methyl, especially hydrogen.
In a preferred embodiment R6 represents hydrogen, hydroxy, fluoro, methyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In another embodiment each of R7 to R10 represents hydrogen, hydroxy, fluoro, methyl, ethyl, isopropyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In a preferred embodiment R7 represents hydrogen, hydroxy, fluoro, methyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In a preferred embodiment R8 represents hydrogen, methyl or ethyl, more preferably hydrogen or methyl.
In a preferred embodiment R9 represents hydrogen, fluoro, methyl, ethyl, isopropyl, tert-butyl, propenyl (especially allyl) or methoxy.
In a preferred embodiment R10 represents hydrogen or methoxy, more preferably hydrogen.
In a further embodiment three of R3 to R6 represent hydrogen and the remaining one, preferably R4 or R6, is selected from the groups as defined above, preferably hydroxy, fluoro, methyl, ethyl, isopropyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In a further embodiment two of R3 to R6 represent hydrogen and the remaining two, preferably R4 and R6 or R5 and R6, are independently selected from the groups as defined above, preferably methyl, methoxy or propenyl (especially allyl).
In a further embodiment three of R7 to R10 represent hydrogen and the remaining one, preferably R7, R8 or R9, is selected from the groups as defined above, preferably hydroxy, fluoro, methyl, ethyl, isopropyl, n-hexyl, propenyl (especially allyl), methoxy or ethoxy.
In a further embodiment two of R7 to R10 represent hydrogen and the remaining two, preferably R7 and R9, are independently selected from the groups as defined above, preferably methyl or methoxy.
In a preferred embodiment there is provided a compound of formula (I) as defined above wherein R1, R2, R3, R8 and R10 each represent hydrogen; R4 and R9 are independently selected from hydrogen and methoxy; R5 is selected from hydrogen and methyl; R6 and R7 are independently selected from hydrogen, methyl and methoxy; and X represents acetate or chloride, more especially acetate; or a solvate thereof.
It is to be understood that the present invention covers all combinations of particular and preferred groups as described above.
In a particularly preferred embodiment there is provided a compound of formula (I) as defined above selected from the group comprising:
6,6xe2x80x2-bis(2-Hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3-ethoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3-methoxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-5-fluorophenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3,5-dimethylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-3-fluorophenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2,3-Dihydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-6-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(2-Hydroxy-5-t-butylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(5-Allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(3-Allyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-bis(3-Hexyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methylphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3-Fluoro-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-4-methylphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-hexylphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3-Hexyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(5-Fluoro-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(5-allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(5-allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(5-ethyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(2-hydroxy-5-isopropylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(4-ethyl-2-hydroxy phenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
and solvates thereof, particularly pharmaceutically acceptable solvates thereof
In a further particularly preferred embodiment there is provided a compound of formula (I) as defined above selected from the group comprising:
6,6xe2x80x2-bis(2-Hydroxyphenyl)-2,2xe2x80x2-bipydine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-3-ethoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-3-methoxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-5-fluorophenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-3,5-dimethylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-3-fluorophenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2,3-Dihydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-6-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(2-Hydroxy-5-t-butylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(5-Allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(3-Allyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-bis(3-Hexyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methylphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese (Ill) chloride;
6-(3-Fluoro-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-4-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-4-methylphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-hexylphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine manganese(III)chloride;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(3-Hexyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(5-Fluoro-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-3-methoxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(5-allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-3-methoxyphenyl)-6xe2x80x2-(5-allyl-2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(5-ethyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(2-hydroxy-5-isopropylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(4-ethyl-2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
and solvates thereof, particularly pharmaceutically acceptable solvates thereof.
In an especially preferred embodiment there is provided a compound of formula (I) as defined above selected from the group comprising:
6,6xe2x80x2-Bis(2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6,6xe2x80x2-Bis(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)acetate;
and solvates thereof, particularly pharmaceutically acceptable solvates thereof.
In a further especially preferred embodiment there is provided a compound of formula (I) as defined above selected from the group comprising: solvates thereof, particularly pharmaceutically acceptable solvates thereof
6,6xe2x80x2-Bis(2-hydroxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(2-hydroxy-3-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6,6xe2x80x2-Bis(2-hydroxy-3-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(3,4-Dimethyl-2-hydroxyphenyl)-6xe2x80x2-(2-hydroxy-5-methoxyphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
6-(2-Hydroxy-5-methoxyphenyl)-6xe2x80x2-(2-hydroxy-5-methylphenyl)-2,2xe2x80x2-bipyridine-manganese(III)chloride;
and solvates thereof, particularly pharmaceutically acceptable solvates thereof
According to a further aspect of the present invention there is provided a process for the preparation of a compound of formula (I) as defined above which comprises the reaction of a compound of formula (II) 
wherein R1 to R10 are as defined above, with an appropriate manganese reagent containing the anion X.
Thus, for example to prepare the compounds of formula (I) in which X represents acetate the reaction would be between the ligand of formula (II) and manganese(II)acetate tetrahydrate. Suitable manganese reagents can be used to prepare certain compounds of formula (I) in which X is otherwise defined; however, reaction with certain manganese reagents do not result in complexation as is the case, for example, with manganese(II)chloride. The reaction is typically carried out in an appropriate solvent, such as methanol, ethanol, DMF, isopropyl alcohol or butanol at temperatures up to the reflux temperature of the solvent, but preferably at temperatures between 0 and 25xc2x0 C.
Alternatively, compounds of formula (I) in which X represents acetate can be converted using appropriate reagents to compounds of formula (I) in which X is otherwise defined. For example, exchange of X from acetate to chloride can be achieved by reaction with sodium chloride, suitably using a 5%-15% aqueous solution, the reaction typically being carried out in an aqueous, methanolic or ethanolic solution at temperatures up to the reflux temperature of the solvent, but preferably at temperatures between 0 and 25xc2x0 C.
The compounds of formulae (II), wherein R3 to R6 are identical respectively to R10 to R7 (i.e. the two phenyl rings are substituted identically), may be prepared by reaction of the corresponding bipyridine derivative of formula (III) 
wherein R1 and R2 are as defined above and L1 and L2 are each, independently, a suitable leaving group, with the boronic acid derivative of formula (IV) 
wherein R3 to R6 are as defined above; and Ra and Rb represent hydrogen or C1-6 alkyl; or Ra and Rb are linked to form a straight-chain or branched C2-6 alkylene group.
Typically the reaction is carried out in an appropriate solvent such as propanol, 1,2-dimethoxyethane, ethanol or toluene at a temperature up to, but preferably at, the reflux temperature of the solvent; the reaction can typically take from between 2 to 24 hours. The reaction is typically performed in the presence of a base, such as sodium carbonate or triethylamine, and in the presence of a suitable palladium reagent, such as tetrakis(triphenylphosphine) palladium, bis(triphenylphosphine)palladium(II)chloride or [1,4-bis(diphenylphosphino)butane]palladium(II)chloride.
L1 and L2 are each, independently, preferably halo, more preferably chloro, bromo or iodo, most preferably bromo.
Alternatively, the compounds of formula (II) may be prepared by reaction of the bipyridine derivative of formula (V) 
wherein R1, R2, R7 to R10 and L2 are as defined above, with the boronic acid derivative of formula (IV) as defined above.
Alternatively, the compounds of formula (II) may be prepared by reaction of the bipyridine derivative of formula (VI) 
wherein R1, R2, R3 to R6 and L1 are as defined above, with the boronic acid derivative of formula (VII) 
wherein R7 to R10, Ra and Rb are as defined above.
These reactions to prepare the compounds of formulae (II) are typically carried out under similar conditions to the reaction between the compounds of formulae (III) and (IV) as described above.
The compound of formula (V) as defined above may be prepared by a similar reaction of a compound of formula (III) as defined above with a compound of formula (VII) as defined above. The compound of formula (VI) as defined above may be prepared by a similar reaction of a compound of formula (III) as defined above with a compound of formula (IV) as defined above. In these reactions, however, the compound of formula (III) is in excess to ensure that predominantly displacement of only one of leaving groups L1 or L2 occurs.
Where R1 and R2 are different, reaction of the compound of formula (III) with a compound of formula (IV) or (VI) will in fact result in the preparation of two isomeric products wherein respectively each leaving group L1 and L2 reacts, even though an excess of the compound of formula (III) means the displacement of both leaving groups is minimized; the relative yields of the two isomers will be dependent on the respective natures of R1 and R2 since this will influence the relative displacability of the leaving groups L1 and L2 on each pyridine ring. Reaction Scheme 1 below is a representative illustration of this aspect. 
In Reaction Scheme 1, separation of the isomeric compounds of formulae (V/VI) could be carried out, for example by flash chromatography, prior to their subsequent reaction. Alternatively, the mixture of isomeric complexes of formula (I) could be separated, for example by HPLC. As a further alternative, the mixture of isomeric compounds of formula (II) could be separated prior to their subsequent complexation reaction (although this will in general be more difficult and thus less preferred, given their typical solubility characteristics).
The compounds of formulae (III), (IV) and (VII) referred to above are either readily available or may be readily synthesised by those skilled in the art using conventional methods of organic synthesis.
Reaction Schemes 2 and 3 below are representative illustrations of possible methods for the preparation of compounds of formula (III). Reagents and reaction conditions for the individual steps in these Schemes will be well-known to the person skilled in the art. The following references are particularly pertinent: Rodriguez-Ubis, J C et al. (1997) Helv. Chiml. Acta 80: 86-96; Neumann U et al. (1989) Chem. Ber. 122: 589-591. 
The compounds of formulae (IV) and (VII) are in general prepared by reaction of an appropriately protected phenol derivative with a borane reagent as illustrated in the general synthetic procedures and specific Examples described below.
Various intermediate compounds used in the above-mentioned processes, including but not limited to certain of the compounds of formulae (II), (III), (IV), (V), (VI) and (VII), as illustrated above, are novel and thus represent a further aspect of the present invention.
In particular, a further aspect of the present invention is intermediate compounds of formula (II) as defined above; with the exception of 6,6xe2x80x2-Bis(2-hydroxyphenyl)-2,2xe2x80x2-bipyridine.
A further aspect of the present invention is intermediate compounds of formula (III) as defined above; with the exception of 6,6xe2x80x2-dibromo-2,2xe2x80x2-bipyridyl and 6,6xe2x80x2-dibromo-4,4xe2x80x2-dimethoxy-2,2xe2x80x2-bipyridyl.
A further aspect of the present invention is intermediate compounds of formula (IV) or (VII) as defined above; with the exception of 2-hydroxyphenylboronic acid.
A further aspect of the present invention is intermediate compounds of formula (V) or (VI) as defined above.
Whilst it is possible for the compounds of the present invention to be administered as the complex per se, it is preferred to present them in the form of a pharmaceutical formulation.
Pharmaceutical formulations can be adapted for administration by any appropriate route, for example by the oral (including buccal or sublingual), rectal, nasal, topical (including buccal, sublingual or transdermal), vaginal or parenteral (including subcutaneous, intramuscular, intravenous or intradermal) route. Such formulations can be prepared by any method known in the art of pharmacy, for example by bringing into association the active ingredient with the carrier(s), diluent(s) or excipient(s).
Thus, according to a further aspect of the present invention there is provided a pharmaceutical formulation comprising at least one compound of formula (I) or a solvate thereof together with one or more pharmaceutically acceptable carriers, diluents or excipients.
Pharmaceutical formulations may be presented in unit dose forms containing a predetermined amount of active ingredient per unit dose. Such a unit may contain for example 1 xcexcg to 10 g, preferably 0.01 mg to 1000 mg, more preferably 0.1 mg to 250 mg, of a compound of formula (I) or a solvate thereof, depending on the condition being treated, the route of administration and the age, weight and condition of the patient.
Pharmaceutical formulations adapted for oral administration may be presented as discrete units such as capsules or tablets; powders or granules; solutions or suspensions in aqueous or non-aqueous liquids; edible foams or whips; or oil-in-water liquid emulsions or water-in-oil liquid emulsions. Typically, tablet or capsules will be prepared to contain from 1 mg to 1,000 mg, preferably 2.5 mg to 250 mg of active ingredient per unit dose.
Pharmaceutical formulations adapted for transdermal administration may be presented as discrete patches intended to remain in intimate contact with the epidermis of the recipient for a prolonged period of time. For example, the active ingredient may be delivered from the patch by iontophoresis as generally described in Pharmaceutical Research, 3(6), 318 (1986).
Pharmaceutical formulations adapted for topical administration may be formulated as ointments, creams, suspensions, lotions, powders, solutions, pastes, gels, sprays, aerosols or oils.
For treatments of the eye or other external tissues, for example mouth and skin, the formulations are preferably applied as a topical ointment or cream. When formulated in an ointment, the active ingredient may be employed with either a paraffinic or a water-miscible ointment base. Alternatively, the active ingredient may be formulated in a cream with an oil-in-water cream base or a water-in-oil base.
Pharmaceutical formulations adapted for topical administrations to the eye include eye drops wherein the active ingredient is dissolved or suspended in a suitable carrier, especially an aqueous solvent.
Pharmaceutical formulations adapted for topical administration in the mouth include lozenges, pastilles and mouth washes.
Pharmaceutical formulations adapted for rectal administration may be presented as suppositories or as enemas; rectal ointments and foams may also be employed.
Pharmaceutical formulations adapted for nasal administration wherein the carrier is a solid include a coarse powder having a particle size for example in the range 20 to 500 microns which is administered in the manner in which snuff is taken, i.e. by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable formulations wherein the carrier is a liquid, for administration as a nasal spray or as nasal drops, include aqueous or oil solutions of the active ingredient.
Pharmaceutical formulations adapted for administration by inhalation include fine particle dusts or mists which may be generated by means of various types of metered dose pressurized aerosols, nebulizers or insufflators. Spray compositions may, for example, be formulated as aerosols delivered from pressurised packs, such as a metered dose inhaler, with the use of a suitable liquified propellant. Capsules and cartridges for use in an inhaler or insufflator, of for example gelatine, may be formulated containing a powder mix for inhalation of a compound of the invention and a suitable powder base such as lactose or starch. Each capsule or cartridge may generally contain between 1 xcexcg-10 mg of the compound of formula (I) or a solvate thereof. Aerosol formulations are preferably arranged so that each metered dose or xe2x80x9cpuffxe2x80x9d of aerosol contains 1 xcexcg-2000 xcexcg, preferably about 1 xcexcg-500 xcexcg of a compound of formula (I) or a solvate thereof. Administration may be once daily or several times daily, for example 2, 3, 4 or 8 times, giving for example 1, 2 or 3 doses each time. The overall daily dose with an aerosol will generally be within the range 10 xcexcg-10 mg, preferably 100 xcexcg-2000 xcexcg. The overall daily dose and the metered dose delivered by capsules and cartridges in an inhaler or insufflator will generally be double those with aerosol formulations.
Pharmaceutical formulations adapted for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations.
Pharmaceutical formulations adapted for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain antioxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets.
Further examples of suitable pharmaceutical formulations are given in the prior art patent documents referred to above, particularly in WO96/40149.
As used herein, an xe2x80x9cantioxidantxe2x80x9d is a substance that, when present in a mixture or structure containing an oxidizable substrate biological molecule, significantly delays or prevents oxidation of the substrate biological molecule. Antioxidants can act by scavenging biologically important reactive free radicals or other reactive oxygen species (xe2x80xa2O2xe2x88x92, H2O2, xe2x80xa2OH, HOCl, ferryl, peroxyl, peroxynitrite, and alkoxyl), or by preventing their formation, or by catalytically converting the free radical or other reactive oxygen species to a less reactive species. An antioxidant compound of the present invention generally has detectable SOD, CAT and/or POD activity. A compound of the present invention has antioxidant activity if the complex, when added to a cell culture or assay reaction, produces a detectable decrease in the amount of a free radical, such as superoxide, or a nonradical reactive oxygen species, such as hydrogen peroxide, as compared to a parallel cell culture or assay reaction that is not treated with the complex. The relative amount of free radical species is often determined by detection of a secondary indicator (e.g., an oxidized substrate; peroxidized lipid, cytochrome C).
As used herein, xe2x80x9cfree radical-associated diseases or conditionsxe2x80x9d refers to a pathological condition of an individual that results at least in part from the production of or exposure to free radicals, particularly oxyradicals, and other reactive oxygen species in vivo. It is evident to those of skill in the art that most pathological conditions are multifactorial, in that multiple factors contributing to the disease state are present, and that assigning or identifying the predominant causal factor(s) for any individual pathological condition is frequently extremely difficult. For these reasons, the term xe2x80x9cfree radical associated diseasexe2x80x9d encompasses pathological states that are recognized in the art as being conditions wherein damage from free radicals or reactive oxygen species is believed to contribute to the pathology of the disease state, or wherein administration of a free radical inhibitor (e.g., desferrioxamine), scavenger (e.g., tocopherol, glutathione), or catalyst (e.g., SOD, catalase) is shown to produce a detectable benefit by decreasing symptoms, increasing survival, or providing other detectable clinical benefits in treating or preventing the pathological state. For example but not limitation, the disease states discussed herein are considered free radical-associated diseases (e.g., ischemic reperfusion injury, inflammatory diseases, systemic lupus erythematosus, myocardial infarction, stroke, traumatic hemorrhage, spinal cord trauma, Crohn""s disease, autoimmune diseases (e.g., rheumatoid arthritis, diabetes), cataract formation, uveitis, emphysema, gastric ulcers, oxygen toxicity, neoplasia, undesired cell apoptosis, radiation sickness, and other pathological states discussed above, such as toxemia and acute lung injury). Such diseases can include xe2x80x9capoptosis-related ROSxe2x80x9d which refers to reactive oxygen species (e.g., O2xe2x88x92, HOOH) which damage critical cellular components (e.g., lipid peroxidation) in cells stimulated to undergo apoptosis, such apoptosis-related ROS may be formed in a cell in response to an apoptotic stimulus and/or produced by non-respiratory electron transport chains (i.e., other than ROS produced by oxidative phosphorylation).
The compounds of formula (I) and solvates thereof have antioxidant and/or free radical scavenging properties as demonstrated hereinafter by their SOD, CAT or POD mimetic activity.
The present invention thus also provides compounds of formula (I) and solvates thereof for use in medical therapy. The compounds of the present invention are of potential utility in treating and preventing free radical associated diseases and conditions which involve a component of oxidative stress including, for example, Alzheimer""s disease, dementia, Parkinson""s disease, Lou Gehrig disease, motor neurone disorders, Huntington""s disease, cancer, multiple sclerosis, systemic lupus erythematosus, scleroderma, eczema, dermatitis, delayed type hypersensitivity, psoriasis, gingivitis, adult respiratory distress syndrome, septic shock, multiple organ failure, asthma, allergic rhinitis, pneumonia, emphysema, chronic bronchitis, AIDS, inflammatory bowel disease, pancreatitis, transplantation rejection, atherosclerosis, hypertension, congestive heart failure, myocardial ischemic disorders, angioplasty, endocarditis, retinopathy of premanurity, cataract formation, uveitis, rheumatoid arthritis and osteoarthritis.
The compounds of formula (I) and solvates thereof are also of potential utility in treating and preventing free radical-associated diseases or conditions as referred to above.
In preferred embodiments, the compounds of the present invention and formulations thereof may used for preventing, arresting, or treating (1) neurological damage such as Parkinson""s disease or Alzheimer""s disease, (2) cardiac tissue necrosis resulting from cardiac ischemia, (3) autoimmune neurodegeneration (e.g., encephalomyelitis), (4) acute lung injury such as in sepsis and endotoxemia, and (5) neuronal damage resulting from ischemia (e.g., stroke, drowning, brain surgery) or trauma (e.g., concussion or cord shock).
The compounds of the present invention and formulations thereof may also have utility for the following additional indications: (1) for preventing ischemic/reoxygenation injury in a patient, (2) for preserving organs for transplant in an anoxic, hypoxic, or hyperoxic state prior to transplant, (3) for protecting normal tissues from free radical-induced damage consequent to exposure to ionizing radiation and/or chemotherapy, as with bleomycin, (4) for protecting cells and tissues from free radical-induced injury consequent to exposure to xenobiotic compounds which form free radicals, either directly or as a consequence of monooxygenation through the cytochrome P-450 system, (5) for enhancing cryopreservation of cells, tissues, organs, and organisms by increasing viability of recovered specimens and (6) for prophylactic administration to prevent carcinogenesis, cellular senescence, cataract formation, formation of malondialdehyde adducts, HIV pathology (as described below) and macromolecular crosslinking, such as collagen crosslinking.
The compounds of the present invention and formulations thereof may also be of benefit to patients who are infected with a human immunodeficiency virus (e.g., HIV-1) or who are at risk of becoming infected with a human immunodeficiency virus. The antioxidant compounds of the present invention may prevent or inhibit the induction of HIV-1 replication in CD4+ lymphocytes by tumor necrosis factor (TNF or other inflammatory mediators) and/or prevent damage to or death of CD4+ cells as a consequence of HIV-1 infection. Without wishing to be bound by any particular theory of HIV-1 replication or HIV-1 pathogenesis, it is believed that administration of an antioxidant complex can inhibit and/or slow the development of HIV-1 related pathology and/or can reduce the rate of decline of the CD4+ lymphocyte population in HIV infected individuals. The antioxidant compounds of the present invention may also inhibit pathology resulting from excessive or inappropriate levels of TNF or other inflammatory mediators, both in AIDS and in other conditions (e.g., septic shock). Frequently, a dosage of about 50 to 5000 mg will be administered to a patient with HIV and/or with excessive or inappropriate levels of TNF, either in single or multiple doses, to reduce or retard the development of pathology and clinical symptoms. Antioxidant compounds of the present invention may be administered therapeutically to treat viral diseases other than HIV.
The compounds of the present invention and formulations thereof may also have utility in enhancing the recovery of skin of a warm-blooded animal from wounds, such as surgical incisions, bums, inflammation or minor irritation due to oxidative damage, etc.
A further aspect of the invention provides a method of prophylaxis or treatment of a human or animal subject suffering from a diseases or condition which involves a component of oxidative stress and/or a free radical-associated disease or condition which comprises administering to said subject an effective amount of a compound of formula (I) or a solvate thereof.
A further aspect of the present invention provides the use of a compound of formula (I) or a solvate thereof in therapy.
A further aspect of the present invention provides the use of a compound of formula (I) or a solvate thereof in the preparation of a medicament for the prophylaxis or treatment of a disease or condition which involves a component of oxidative stress and/or a free radical-associated disease or condition.
A further aspect of the present invention provides the use of a compound of formula (I) or a solvate thereof in the preparation of a medicament for the prophylaxis or treatment of the specific disorders and conditions referred to above.
The compounds of the present invention and formulations thereof can be administered for prophylactic and/or therapeutic treatments. In therapeutic application, formulations are administered to a patient already affected by the particular free radical associated disease, in an amount sufficient to cure or at least partially arrest the condition and its complications. An amount adequate to accomplish this is defined as a xe2x80x9ctherapeutically effective dosexe2x80x9d or xe2x80x9cefficacious dose.xe2x80x9d Amounts effective for this use will depend upon the severity of the condition, the general state of the patient, and the route of administration, but generally range from about 1 xcexcg to about 10 g of antioxidant compounds of the present invention per dose, with dosages of from 0.1 mg to 2000 mg per patient being more commonly used.
In prophylactic applications, formulations containing the antioxidant compound of the present invention or cocktails thereof are administered to a patient not already in a disease state to enhance the patient""s resistance or to retard the progression of disease. Such an amount is defined to be a xe2x80x9cprophylactically effective dose.xe2x80x9d In this use, the precise amounts again depend upon the patient""s state of health and general level of immunity, but generally range from 1 xcexcg to 10 g per dose, especially 0.01 mg to 1000 mg per patient.
As indicated above, a typical formulation of a compound of the present invention will contain between about 0.1 and 250 mg of the complex in a unit dosage form. Single or multiple administrations of the formulations can be carried out with dose levels and dosing pattern being selected by the treating physician.
In general, for treatment of free radical-associated diseases, a suitable effective dose of the antioxidant compound of the present invention will be in the range of 0.01 micrograms (xcexcg) to 1000 milligram (mg) per kilogram (kg) of body weight of recipient per day, preferably in the range of 0.1 xcexcg to 100 mg per kg of body weight per day, more preferably in the range of 1 xcexcg to 10 mg per kg of body weight per day. For example, 0.2 mg/kg for a 70 kg human adult would result in a daily dose of 14 mg. The desired dosage is preferably presented in one, two, three, four or more subdoses administered at appropriate intervals throughout the day. These subdoses can be administered as unit dosage forms as referred to above.
Kits can also be supplied for use with the compounds of the present invention for use in the protection against or therapy for a free radical-associated disease. Thus, the subject formulation of the present invention may be provided, usually in a lyophilized form or aqueous solution in a container, either alone or in conjunction with additional antioxidant compounds of the present invention of the desired type. The antioxidant compounds are included in the kits with buffers, such as Tris, phosphate, carbonate, etc., stabilizers, biocides, inert proteins, e.g. serum albumin, or the like, and a set of instructions for use. Generally, these materials will be present in less than about 5% wt. based on the amount of antioxidant compounds of the present invention and usually present in total amount of at least about 0.001% based again on the concentration. Frequently, it will be desirable to include an inert extender or excipient to dilute the active ingredients, where the excipient may be present in from about 1 to 99.999% wt. of the total formulation.
The compounds of the present invention may be employed alone or in combination with other therapeutic agents for the treatment of the above-mentioned conditions, and in particular in combination with other antioxidant agents that have SOD activity, catalase activity, peroxidase activity, or are free radical scavengers or inhibitors of free radical formation. Combination therapies according to the present invention thus comprise the administration of at least one compound of formula (I) or a pharmaceutically acceptable solvate thereof and at least one other pharmaceutically active agent. The compound(s) of formula (I) or a solvate thereof and the other pharmaceutically active agent(s) may be administered together or separately and, when administered separately this may occur simultaneously or sequentially in any order. The amounts of the compound(s) of formula (I) or a solvate thereof and the other pharmaceutically active agent(s) and the relative timings of administration will be selected in order to achieve the desired combined therapeutic effect.